1. Field of the Invention
This invention generally relates to heat exchange units and more particularly to an indoor unit of a heat pump including apparatus for controlling air flow in heat exchange relation with the fan motor used to power an indoor fan included as part of the indoor unit.
2. Prior Art
A typical reverse cycle or heat pump air conditioning unit includes a refrigeration circuit having indoor and outdoor heat exchangers as well as a compressor and an expansion device. A reversing valve is provided to direct the flow of refrigerant either directly to the indoor heat exchanger when the unit is operated to provide heating or to the outdoor heat exchanger when it is operated to provide cooling. The refrigeration circuit acts to exchange heat energy between air flowing through the indoor unit, typically, the air being returned to the space to be conditioned and the outdoor ambient in heat exchange relation with the outdoor unit. Hence, thermal energy is transferred between outdoor ambient air and the indoor space based upon the mode of operation of the air conditioning system.
The typical indoor unit for use in a heat pump system includes a heat exchanger serving as the indoor heat exchanger. This heat exchanger is a condenser when the unit is operated in the heating mode discharging thermal energy and an evaporator when the unit is operated in the cooling mode absorbing thermal energy. The typical indoor unit additionally includes a fan for circulating air between the space to be conditioned and the indoor heat exchanger. Conventionally the heat exchanger is mounted within a casing which is connected by duct work to the appropriate portions of the space to be conditioned.
In prior art heat pump systems, the indoor fan motor for powering the indoor fan is located within the casing defining the indoor unit and located within the air flow stream of the air flowing through the unit to the space to be conditioned. During operation the indoor fan motor converts electrical energy into mechanical energy for circulating the air and into thermal energy. This thermal energy is given up to the air flowing in heat exchange relation with the motor adding to the heating capability of the system.
When the heat pump is operated in the cooling mode of operation the thermal energy of the fan is additionally dissipated into the indoor air stream adding to the overall cooling load on the unit. Prior art cooling only devices have avoided this problem by locating the fan motor external to the air stream such that the thermal energy created by operation of the motor is dissipated to a separate heat sink from the air being circulated to the enclosure.
The present arrangement concerns the altering of the indoor air flow path such that heat energy generated by the fan motor is absorbed by the indoor air when the heat pump is operated in the heating mode and is discharged to a separate heat sink when the heat pump is operated in the cooling mode. Hence, the energy utilized by the fan motor which is converted to thermal energy is utilized to increase the heating capability of the unit when it is operating in the heating mode and is dissipated outside the indoor air flow stream to not add to the cooling load when the unit is in the cooling mode of operation. Specific apparatus is disclosed herein for effecting a change in the indoor air flow path to obtain appropriate utilization of the thermal energy generated by the indoor fan motor. As set forth herein, the indoor fan motor is mounted on a bracket extending partially within the casing defining the indoor unit. Air flow through the indoor unit flows in heat exchange relation with the motor unless a cover is placed about the bracket preventing air flow to the motor. An additional enclosure is provided for covering the exterior of the motor when the unit is operating in the heating mode such that thermal energy from the motor is not transferred to air outside the casing. When the unit is operated in the cooling mode the motor bracket is covered such that indoor air is not in heat exchange relation with the motor and the enclosure covering the portion of the motor extending outside is removed such that heat energy from the motor is dissipated to the heat sink surrounding the indoor unit. This heat sink may typically be the air of the basement or an enclosure, garage, attic or some other space where added heat energy during the cooling mode is not a significant factor to the homeowner.